The present invention is directed to a method and an arrangement for accomplishing assembly substitution actions during ongoing operation of a bus system. Assembly substitution action refers to the insertion or removal of assemblies (such as circuit boards), as well as, substitution of one assembly with another assembly.
The problem arises in a bus system, that is in operation, that entirely new assemblies must be introduced into the bus system, existing assemblies must be entirely removed or must be replaced by others, i.e. that assembly substitution actions are necessary. In many prior art bus systems currently being utilized, assembly substitution actions are simply not possible during ongoing operation. As a rule, a computer system must be disconnected before the substitution action and then reconnected after the substitution action.
The problem when inserting or removing assemblies during ongoing operation of a bus system is that the connecting contacts of the plug-type connectors for electrically connecting the assemblies to the bus system can be affected when inserting or removing the assemblies under tension. These effects can lead to oxidation of the connecting contacts of the plug-type connector, resulting in destruction of assembly components or disturbance of bus signals.
The problems are usually so serious when inserting assemblies during ongoing operation of a bus system that they cannot be overlooked. The removing of assemblies is in fact possible under tension under certain circumstances but is nonetheless not to be recommended. The individual connecting contacts of a plug-type connector allocated to one another have capacitances with which the voltage conditions on the assemblies are maintained for a time after the connecting contacts of the plug-type connector separate when removing the assemblies, these voltage conditions then slowly decaying. The capacitances are usually discharged when inserting the assemblies, so that a maximum voltage gradient exists between the individual connecting contacts before the insertion of an assembly. This leading to a sudden change of the electrical conditions for the bus system and the respective assembly with the afore-mentioned, disadvantageous effects.
The oxidation of connecting contacts is produced, for example, due to spark formation when inserting or removing an assembly. The destruction of assembly parts is caused, for example, by incorrect current flow when the supply voltage is connected when inserting an assembly before the connecting contacts for the signal transmission paths have closed. Disturbances of bus signals can always occur when an assembly causes a change of prevailing electrical conditions in a relatively short time.
The afore-mentioned capacitances of the connecting contacts are further increased by the blocking capacitors that are usually arranged on the assemblies. The situation when removing an assembly may thereby in fact be improved under certain conditions but it is deteriorated during insertion.
At least some of the recited problems exist not only when the supply voltage of the bus system is applied but also, because of the existing capacitances, when only the supply voltage of the assemblies is disconnected before insertion or removal of the assembly during ongoing operation. The bus system is basically still active and is susceptible to disturbance, particularly with respect to the signal transmission paths as set forth above.
Since the bus systems used in industry are usually based on a standardized interface, the bus systems cannot simply be modified as desired in order to be made serviceable for assembly substitution actions during ongoing operations. The underlying, standardized interfaces must not be modified, so that the replaceability of products of various manufacturers continues to be guaranteed.